1. Field of the Invention
The present invention relates to a method and a system for mounting electric components on a printed-wiring board to produce printed circuit boards.
2. Related Art Statement
There are various manners of mounting electric components (xe2x80x9cECsxe2x80x9d) on a printed-wiring board. For example, Japanese Patent Document TOKU-KAI-HEI No. 6(1994)-196546 discloses an EC mounting system which includes a movable member which is movable to an arbitrary position on a horizontal plane; a main moving device which moves the movable member; a rotatable body which is attached to the movable member such that the rotatable body is rotatable about a vertical axis line; and a plurality of suction nozzles which are supported by the rotatable body such that the suction nozzles are provided along a circle whose center is located on the axis line of the rotatable body and such that each of the suction nozzles is not rotatable relative to the rotatable body and is movable relative to the body in a direction parallel to the axis line of the body. In the EC mounting system, owing to combination of the movement of the movable member and the rotation of the rotatable body, the suction nozzles sequentially suck and hold respective ECs, and sequentially mount the ECs on respective EC-mount locations on a printed-wiring board.
The above EC mounting system further includes an image taking device which is fixed in position. When the suction nozzles all holding the respective ECs pass by the image taking device, the image taking device take respective images of the ECs held by the suction nozzles, and the mounting system calculates, based on image data representing the taken images, position errors of the EC held by each of the suction nozzles. The position errors include respective position errors of the center of the EC in two directions perpendicular to each other on a horizontal plane, and a rotation-position error of the EC about a vertical axis line of the each suction nozzle. The position errors of the center of the EC are corrected by correcting respective distances of movement of the movable member in the two directions, and the rotation-position error is corrected by rotating the rotatable body. Thus, the EC is mounted with a correct rotation position at a correct EC-mount location on the printed-wiring board.
However, the above EC mounting system employs a plurality of engaging members corresponding to the plurality of suction nozzles, respectively, and revolves the engaging members with the corresponding suction nozzles, so that whichever rotation phase each of the suction nozzles may take, the corresponding engaging member can engage the each suction nozzle, thereby move the nozzle toward the printed-wiring board supported by a board supporting device, and mount the EC on the board. Thus, a great mass is moved with the movable member and accordingly it is difficult to start and/or stop the movable member so quickly, which leads to limiting the improvement of EC mounting efficiency.
The above problem that a great movement mass limits the improvement of EC mounting efficiency is encountered by not only the EC mounting system disclosed by the above-indicated Japanese Patent Document but also an EC mounting system of a type (hereinafter, referred to as the rotatable-body-moving-type EC mounting system) which includes a rotatable body and a plurality of suction nozzles supported by the rotatable body, and which moves the rotatable body along a plane perpendicular to an axis line of rotation of the body and thereby mounts ECs held by the suction nozzles on a printed-wiring board.
Moreover, there is an EC mounting system of a type which includes a rotatable body and a plurality of suction nozzles supported by the rotatable body, and which does not move the rotatable body but moves a printed-wiring board to mount ECs held by the suction nozzles on the board. In this EC mounting system, if a plurality of engaging members are employed and provided on the rotatable body, for moving the corresponding suction nozzles toward the printed-wiring board supported by a board supporting device, the rotatable body is subjected to an increased moment of inertia. Thus, it is difficult to start and/or stop the rotatable body so quickly, which leads to limiting the improvement of EC mounting efficiency.
The present invention provides an electric-component mounting method and an electric-component mounting system which have one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (22). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needled. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited.
(1) According to a first feature of the present invention, there is provided a method of sequentially mounting, on a printed-wiring board supported by a board supporting device, a plurality of electric components which are sucked and held by respective ends of a plurality of suction nozzles which are supported by a rotatable body such that the suction nozzles are provided along a circle whose center is located on an axis line of the rotatable body and such that each of the suction nozzles is not rotatable relative to the rotatable body and is movable relative to the body in a direction parallel to the axis line of the body, the rotatable body being attached to a movable member which is movable to an arbitrary position on a movement plane parallel to the printed-wiring board supported by the board supporting device, such that the rotatable body is rotatable about the axis line thereof perpendicular to the movement plane, the method comprising the steps of sequentially positioning, owing to combination of the rotation of the rotatable body and the movement of the movable member, the respective electric components sucked and held by the suction nozzles, at respective positions opposed to respective predetermined locations on the printed-wiring board supported by the board supporting device, such that at least two of the electric components thus positioned take different rotation positions, rotating, concurrently with the rotation of the rotatable body, an engaging member common to the plurality of suction nozzles, to a position corresponding to one of the suction nozzles that holds the electric component to be mounted next, and moving, in the direction parallel to the axis line of the rotatable body, the engaging member to engage the one suction nozzle, so that the one suction nozzle is moved toward the board supporting device and the electric component held by the one suction nozzle is mounted on the printed-wiring board. In the present electric-component (xe2x80x9cECxe2x80x9d) mounting method, owing to combination of the rotation of the rotatable body and the movement of the movable member, the respective ECs sucked and held by the suction nozzles are sequentially positioned at respective positions opposed to respective predetermined locations on the printed-wiring board supported by the board supporting device, in such a manner that two or more of the suction nozzles holding the respective ECs are positioned at two or more different rotation phases of the rotatable body. The suction nozzles are not rotatable relative to the rotatable body. Therefore, if two or more of the suction nozzles are positioned at two or more different rotation phases of the rotatable body, the two or more suction nozzles have different rotation positions about respective axis lines thereof, and accordingly the respective ECs held by the two or more suction nozzles have different rotation positions. Therefore, if each of the two or more suction nozzles is moved toward the board supporting device, the respective ECs held by the two or more suction nozzles are mounted with the different rotation positions on the printed-wiring board. Though, in the present method, each of the two or more suction nozzles may be revolved to change the rotation position of the EC held by the each suction nozzle, the engaging member can be rotated to a rotation phase corresponding to one of the two or more suction nozzles that holds the EC to be mounted next, and can move the one suction nozzle toward the board supporting device. Thus, in the present method, the common or single engaging member is used to move each of the two or more suction nozzles positioned at the different rotation phases of the rotatable body, toward the board supporting device. Accordingly, the present method may be performed by a device which has a simplified construction, which contributes to decreasing the mass of a portion of the device that is moved with the movable member. Therefore, the movable member can be moved with high accuracy and at high speeds, which leads to improving the EC mounting efficiency. This effect is the most advantageous, in the case where each of the suction nozzles can be moved, at an arbitrary rotation phase of the rotatable body, toward the board supporting device. In the last case, the present method may be performed by the EC mounting system, disclosed by the above-indicated Japanese Patent Document, in which the plurality of suction nozzles are provided with the respective exclusive engaging members and the engaging members are revolved with the suction nozzles. However, the prior system has a complicated construction and a great mass, and accordingly it is difficult to move the movable member with high accuracy and at high speeds. In contrast, in the present method, the engaging member is commonly used for the plurality of suction nozzles, and accordingly each of the suction nozzles can be moved, at an arbitrary rotation phase, toward the board supporting device, without complicating the construction of the device. In addition, the mass of a portion of the device that is moved with the movable member can be reduced, and accordingly the EC mounting efficiency can be improved by moving the movable member with high accuracy and at high speeds.
(2) According to a second feature of the present invention that includes the first feature (1), the method further comprising simultaneously taking, with an image taking device, respective images of the electric components held by the suction nozzles, processing the taken image of the electric component held by each of the suction nozzles, to determine at least one position error of the electric component held by the each suction nozzle, and controlling the rotation of the rotatable body and the movement of the movable member to eliminate the position error. The at least one position error of the EC includes at least one of a rotation-position error of the EC and a position error of the center of the EC. The image taking device may be a surface-image taking device which has an image-take surface capable of simultaneously forming the respective images of the ECs thereon. The surface-image taking device may be moved with the rotatable body, according to the third feature (3) described below, or may be moved relative to the rotatable body. In the former case, the respective images of the ECs can be taken without stopping the movement of the rotatable body. In the latter case, the surface-image taking device may be fixed in position, or may be provided on a first member which is movable relative to a second member which is moved with the rotatable body. In either case, the images of the ECs can be taken without stopping the movement of the rotatable body, by, e.g., employing a short exposure time, but the images of the ECs may be taken in the state in which the rotatable body is stopped. The image taking device may be a so-called line sensor which includes a number of image-take elements arranged along a straight line extending in a direction intersecting a direction of movement of the rotatable body, and which is moved relative to the rotatable body. As the rotatable body is moved relative to the line sensor, the line sensor takes, at a regular interval of time, images of respective portions of the ECs. Since the ECs are moved while the line sensor repeatedly takes the images of respective portions of the ECs, the line sensor eventually take respective two-dimensional images of all the ECs. Irrespective of how the image taking device may be constructed, after all the suction nozzles suck and hold respective ECs, the image taking device simultaneously takes respective images of the ECs. Thus, the EC mounting efficiency can be improved as compared with the case where, each time one suction nozzle sucks and holds an EC, an image taking device takes an image of the EC, or the case where, while suction nozzles suck and hold respective ECs, an image taking device concurrently takes respective images of the ECs. For example, in the case where an EC-suck position where the suction nozzles suck and hold ECs from an EC supplying device is provided at a rotation phase of the rotatable body, the image taking device is disposed at an EC-image-take position provided at another rotation phase of rotatable body, and the image taking device is moved with the rotatable body, the image taking device can take respective images of the ECs while the ECs are sucked and/or mounted. In the last case, however, it is required that the rotatable body be so sized as to assure that the image taking device does not interfere with the EC supplying device when the ECs are sucked, or with the board supporting device when the ECs are mounted. Accordingly, the rotatable body is required to have a great diameter, which leads to increasing the mass thereof and thereby making it difficult to move the movable member with high accuracy and at high speeds. In contrast, in the present method, the images of ECs are simultaneously taken, and accordingly may be taken at an arbitrary time after all the suction nozzles have sucked and held respective ECs from the EC supplying device and before the ECs are mounted on the printed-wiring board, i.e., may be taken independent of the suction of ECs and/or the mounting of ECs. Thus, the present method does not need increasing the diameter of the rotatable body, and allows the image taking device to be provided without interfering with the EC supplying device or the board supporting device. Thus, the present method can improve the EC mounting efficiency by moving the movable member with high accuracy and at high speeds.
(3) According to a third feature of the present invention that includes the second feature (2), the step of taking the respective images of the electric components comprises taking, during a movement of the rotatable body caused by the movement of the movable member, the respective images of the electric components, with the image taking device which is being moved with the rotatable body. The image taking device may be provided on the movable member so as to be moved with the movable member, or may be provided on a member different from the movable member. In the latter case, an engaging/disengaging device may be employed to engage and disengage the different member with and from the movable member, so that while the image taking device takes the images of the ECs, the image taking device is moved with the rotatable body, and after the image taking device takes the images of the ECs, the different member is disengaged from the movable member, and additionally a returning device may be employed to return the different member to an initial position thereof after the different member is disengaged from the movable member. In the latter case, the present method may not need a reflecting device which causes the images of the ECs to be incident to the image taking device, and which is employed in the EC mounting system according to the twenty-first feature (21) described later. In the present method, the respective images of the ECs can be taken, without stopping the movement of the rotatable body, during a sufficiently long time when the rotatable body is moved toward the printed-wiring board after all the suction nozzles suck and hold the ECs. Thus, excellent images of the ECs can be obtained without sacrificing the EC mounting efficiency. The processing of the thus taken images may be carried out while the rotatable body is moved toward the printed-wiring board or, as needed, while the ECs are mounted on the board.
Each of the above-described first to third features (1) to (3) of the EC mounting method may be combined with one or more of the fourth to twenty-second features (4) to (22) of the EC mounting system that are described below.
(4) According to a fourth feature of the present invention, there is provided an electric-component mounting system, comprising a board supporting device which supports a printed-wiring board; a movable member which is movable to an arbitrary position on a movement plane parallel to the printed-wiring board supported by the board supporting device; a main moving device which moves the movable member; a rotatable body which is attached to the movable member such that the rotatable body is rotatable about an axis line thereof perpendicular to the movement plane; a rotatable-body rotating device which rotates the rotatable body about the axis line thereof; a plurality of suction nozzles which sucks and holds respective electric components and which are supported by the rotatable body such that the suction nozzles are provided along a circle whose center is located on the axis line of the rotatable body and such that each of the suction nozzles is not rotatable relative to the rotatable body and is movable relative to the body in a direction parallel to the axis line of tire body; an engaging member which is rotatable relative to the rotatable body about the axis line of the body and is movable relative to the body in the direction parallel to the axis line of the body, and which includes a nozzle-engaging portion which is engageable with one of the suction nozzles; an engaging-member rotating device which rotates the engaging member to at least two rotation phases of the rotatable body at each of which the nozzle-engaging portion of the engaging member is engageable with the one suction nozzle; an engaging-member moving device which moves the engaging member in the direction parallel to the axis line of the rotatable body, so that the nozzle-engaging portion of the engaging member engages the one suction nozzle and moves the one suction nozzle toward the board supporting device; and a control device which controls the main moving device, the rotatable-body rotating device, the engaging-member rotating device, and the engaging-member moving device. The present EC mounting system can carry out not only the EC mounting method according to the first feature (1), but also different EC mounting methods. The engaging-member rotating device may be one according to the Fifth feature (5) described below, i.e., one which can rotate the engaging member to an arbitrary rotation phase of the rotatable body about the axis line thereof, or may be one which can rotate the engaging member to two predetermined rotation phases of the rotatable body. In the latter case, at least two rotation phases may be assigned to each of the suction nozzles, and the engaging member is rotated to at least two rotation phases corresponding to those at least two rotation phases. The at least two rotation phases of one of the suction nozzles may be identical with, or different from, those of another or the other suction nozzle, or only one of the at least two rotation phases of one suction nozzle may be identical with only one of the at least two rotation phases of another or the other suction nozzle. The engaging-member moving device may be one which moves one suction nozzle toward the board supporting device and permits the one suction nozzle to be moved away from the same, as will be described in DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS. A biasing device such as a spring may be employed to bias the one suction nozzle in a direction away from the board supporting device. In this case, the engaging-member moving device cooperates with the biasing device to provide a nozzle moving device which moves one suction nozzle toward, and away from, the board supporting device. Alternatively, the engaging-member moving device may be one which causes the engaging member Lo be engaged with one suction nozzle such that the engaging member is not movable relative to the one suction nozzle in each of the directions toward and away from the board supporting device, and which moves the one suction nozzle toward and away from the board supporting device. The engaging-member moving device moves one suction nozzle toward the board supporting device, and is moved with the rotatable body. For example, if, for changing the rotation position of the EC held by one suction nozzle, the rotatable body is rotated to change the rotation phase of the one suction nozzle, the engaging member is also rotated to a rotation phase where the engaging member can engage the one suction nozzle and thereby move the one nozzle toward the board supporting device. The engaging member may be one which is common to the plurality of suction nozzles and can move, toward the board supporting device, each of the suction nozzles that may, or may not, have been rotated to change the rotation phase thereof to change the rotation position of the EC held thereby. In the last case, the present system can move, with simple construction, each suction nozzle toward the board supporting device. In the case where the EC mounting system employs the engaging-member rotating device according to the fifth feature (5) and the control device according to the sixth feature (6), the system can change, by rotating the rotatable body, the current rotation position of the EC held by each of the suction nozzles, to any desired rotation position, and can eliminate the rotation-position error of the EC held by the each suction nozzle, as needed. In this case, as compared with the EC mounting system, disclosed in the above-indicated Japanese Patent Document, where the plurality of suction nozzles are provided with the respective exclusive engaging members, the present EC mounting system enjoys a simplified construction and a decreased mass, and accordingly can quickly mount the ECs on the printed-wiring board while changing the respective rotation positions of the ECs held by the suction nozzles. It is desirable that the engaging member he moved toward the ECs or the printed-wiring board by the engaging-member moving device in the same manner both when the ECs are sucked and held by the suction nozzles and when the ECs held by the nozzles are mounted on the printed-wiring board.
(5) According to a fifth feature of the present invention that includes the fourth feature (4), the engaging-member rotating device comprises a rotating device which can rotate the engaging member to an arbitrary rotation phase of the rotatable body about the axis line of the body.
(6) According to a sixth feature of the present invention that includes the fifth feature (5), the control device comprises a positioning control portion which can sequentially position, owing to combination of the rotation of the rotatable body by the rotatable-body rotating device and the movement of the movable member by the main moving device, the respective electric components sucked and held by the suction nozzles, at respective positions opposed to respective predetermined locations on the printed-wiring board supported by the board supporting device, such that each of the electric components thus positioned takes an arbitrary rotation position; and a mounting control portion which controls the engaging-member rotating device to rotate, concurrently with the rotation of the rotatable body, the engaging member to a rotation phase corresponding to the one of the suction nozzles that holds the electric component to be mounted next, which controls the engaging-member moving device to move, in the direction parallel to the axis line of the rotatable body, the engaging member to engage the one suction nozzle, so that the one suction nozzle is moved toward the board supporting device and the electric component held by the one suction nozzle is mounted on the printed-wiring board.
(7) According to a seventh feature of the present invention, there is provided an electric-component mounting system, comprising a board supporting device which supports a printed-wiring board; a rotatable body which is rotatable about an axis line thereof perpendicular to the printed-wiring board supported by the board supporting device; a main moving device which moves at least one of the rotatable body and the board supporting device, relative to the other of the rotatable body and the board supporting device, to an arbitrary position on a movement plane parallel to the printed-wiring board supported by the board supporting device; a rotatable-body rotating device which rotates the rotatable body about the axis line thereof; a plurality of suction nozzles which sucks and holds respective electric components and which are supported by the rotatable body such that the suction nozzles are provided along a first circle whose center is located on the axis line of the rotatable body and such that each of the suction nozzles is movable relative to the body in a direction parallel to the axis line of the body; a nozzle moving device which moves each of the suction nozzles toward, and away from, the board supporting device; and a control device which controls the main moving device, the rotatable-body rotating device, and the nozzle moving device, the nozzle moving device comprising an engaging member which is rotatable relative to the rotatable body about the axis line of the body and is movable relative to the body in the direction parallel to the axis line of the body, and which includes a nozzle-engaging portion which is engageable with one of the suction nozzles, an engaging-member rotating device which rotates the engaging member to at least two rotation phases of the rotatable body at each of which the nozzle-engaging portion of the engaging member is engageable with the one suction nozzle, and an engaging-member moving device which moves the engaging member in the direction parallel to the axis line of the rotatable body, so that the nozzle-engaging portion of the engaging member engages the one suction nozzle and moves the one suction nozzle toward the board supporting device. In the present EC mounting system, the rotatable body may be rotated to change the rotation position of an EC at the time when the EC is sucked and held by one suction nozzle, correct a rotation-position error of an EC held by one suction nozzle, and/or to move an EC held by one suction nozzle to a rotation phase where the EC is the nearest to the corresponding EC-mount position on the printed-wiring board so as to shorten a distance of relative movement of the rotatable body (i.e., the one suction nozzle) and the board supporting device. Anyhow, the engaging member is rotated by the engaging-member rotating device to a rotation phase corresponding to the one suction nozzle, and moves the one nozzle toward the board supporting device. According to the seventh feature (7), the suction nozzles have only to be provided along a circle whose center is located on the axis line of the rotatable body and be each movable relative to the body in a direction parallel to the axis line of the body. Therefore, each suction nozzle may, or may not, be rotatable relative to the rotatable body. In the former case, one or more nozzle rotating devices is or are employed to rotate the suction nozzles relative to the rotatable body. A plurality of nozzle rotating devices may be employed for the plurality of suction nozzles, respectively. In this case, the plurality of nozzle rotating devices may share a portion common to the plurality of suction nozzles. The main moving device has only to move at least one of the rotatable body and the board supporting device relative to the other of the rotatable body and the board supporting device, to an arbitrary position on a movement plane parallel to the printed-wiring board (i.e., a major surface thereof) supported by the board supporting device. Accordingly, the main moving device may be one which moves the rotatable body and the board supporting device in two directions, respectively, which are perpendicular to each other; one which moves only the board supporting device in two directions perpendicular to each other; or one which moves only the rotatable body in two directions perpendicular to each other. The EC mounting system according to the fourth feature (4) corresponds to the EC mounting system according to the seventh feature (7) and wherein the suction nozzles are not rotatable relative to the rotatable body and the main moving device moves only the rotatable body along the movement plane. Each of the rotatable-body rotating device and the engaging-member rotating device may be one which rotates the rotatable body or the engaging member to only one or more predetermined rotation phases, or one which rotates the rotatable body or the engaging member to an arbitrary rotation phase.
(8) According to an eighth feature of the present invention that includes the seventh feature (7), the engaging-member rotating device comprises a rotating device which can rotate the engaging member to an arbitrary rotation phase of the rotatable body about the axis line of the body.
(9) According to a ninth feature of the present invention that includes any one of the fourth to eighth features (4) to (8), the system further comprises a plurality of switch valve devices which are supported by the rotatable body, which correspond to the plurality of suction nozzles, respectively, and each of which comprises at least one switch valve including at least one engageable portion, wherein the engaging member includes at least one valve-engaging portion which is engageable with the at least one engageable portion of the switch valve to switch the switch valve, and wherein the engaging-member rotating device rotates the engaging member to move the valve-engaging portion of the engaging member to a position corresponding to the engageable portion of the switch valve of one of the switch valve devices, and the engaging-member moving device moves the engaging member so that the valve-engaging portion of the engaging member engages the engageable portion of the switch valve of the one switch valve device and thereby switches the one switch valve device. Each of the switch valve devices may be constructed in various manners. For example, each switch valve device may include a plurality of switch valves, as described in DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, or a single switch valve. Even in the latter case, each switch valve device can allow a negative pressure to be supplied to a corresponding suction nozzle and stop the supplying of negative pressure (and additionally allow a positive pressure to be supplied to the corresponding suction nozzle and stop the supplying of positive pressure, as needed). One switch valve may include a plurality of engageable portions, as described in DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, or a single engageable portion. Even in the latter case, the switch valve can perform its switching operation. For example, the valve-engaging portion of the engaging member and the engageable portion of the switch valve are so formed that the motion of the valve-engaging portion in each of opposite directions is transmitted to the engageable portion. The engaging member may include the same number of valve-engaging portion or portions as the number of switch valve or valves of each switch valve device, so that the valve-engaging portion or portions corresponds or correspond to the switch valve or valves, respectively. However, this is not essentially required. For example, the engaging member may include a plurality of valve-engaging portions which correspond to a single switch valve and each of which is selectively engageable with the single switch valve to place the same in a corresponding one of a plurality of switchable states. Alternatively, the engaging member may include a single valve-engaging portion which is selectively engageable with each one of respective engageable portions of a plurality of switch valves of each switch valve device. In the present EC mounting system, the plurality of valve switch devices are employed for the plurality of suction nozzles, respectively, and each of the valve switch devices is switched to supply at least the negative pressure to a corresponding one of the suction nozzles and stop the supplying of negative pressure. The respective switching actions of the switch valve devices are performed by the common engaging member. Thus, the present system can allow and stop, with a simple construction, the supplying of negative pressure (and additionally the supplying of positive pressure, as needed) to each suction nozzle.
(10) According to a tenth feature of the present invention that includes the ninth feature (9), each of the switch valve devices comprises a plurality of switch valves each of which includes the at least one engageable portion, and wherein the valve-engaging portion of the engaging member is selectively engageable, owing to a relative rotation of the engaging member and the rotatable body, with each of the respective engageable portions of the switch valves of the each switch valve device. When ECs are sucked and held by the suction nozzles, the engaging member is rotated to a rotation phase which corresponds to one suction nozzle to be moved thereby toward an EC and simultaneously corresponds to the engageable portion of one of the plurality of switch valves of one switch valve device corresponding to the one suction nozzle, and moves the one suction nozzle toward the EC while switching the one switch valve. When ECs are mounted on the printed-wiring board (xe2x80x9cPWBxe2x80x9d), the engaging member is rotated to a rotation phase which corresponds to one suction nozzle to be moved thereby toward the PWB and simultaneously corresponds to the engageable portion of one of the plurality of switch valves of one switch valve device corresponding to the one suction nozzle, and moves the one suction nozzle toward the PWB while switching the one switch valve. Thus, the engaging member is rotated, for each of the suction nozzles, to each of a plurality of rotation phases at each of which the engaging member is engageable with the engageable portion of a corresponding one of the plurality of switch valves of one switch valve device corresponding to the each suction nozzle, and moves the each suction nozzle toward the EC or the PWB. That is, the single engaging member can switch the plurality of switch valve devices. The tenth feature (10) may be employed independent of any of the fourth to eighth features (4) to (8). That is, the tenth feature (1) may be generally or widely employed in a switch valve which is switchable by engagement thereof with an engaging member and which controls the supplying of negative and/or positive pressure to a suction nozzle.
(11) According to an eleventh feature of the present invention that includes the tenth feature (10), the system further comprises an electric-component supplying device which supplies the electric components to the suction nozzles, wherein the switch valves of the each switch valve device comprise a first switch valve and a second switch valve each of which includes the at least one engageable portion, wherein owing to a movement of the engaging member to engage one of the suction nozzles that corresponds to the each switch valve device and thereby move the one suction nozzle toward the electric-component supplying device, the valve-engaging portion of the engaging member engages the engageable portion of the first switch valve, so that in a terminal portion of the movement of the engaging member, the first switch valve is switched to a state in which the first switch valve permits supplying of a negative pressure to the one suction nozzle, and wherein owing to a movement of the engaging member to engage the one suction nozzle and thereby move the one suction nozzle toward the board supporting device, the valve-engaging portion of the engaging member engages the engageable portion of the second switch valve, so that in a terminal portion of the movement of the engaging member, the second switch valve is switched to a state in which the second switch valve stops the supplying of the negative pressure to the one suction nozzle. When ECs are sucked and held by the suction nozzles, the valve-engaging portion of the engaging member engages the engageable portion of the first switch valve, so that the negative pressure is supplied to one suction nozzle and the one suction nozzle sucks and holds an EC. When ECs are mounted on the PWB, the valve-engaging portion of the engaging member engages the engageable portion of the second switch valve, so that the supplying of negative pressure to one suction nozzle is stopped, the one suction nozzle releases an EC, and the EC is mounted on the PWB. In each case, in a terminal portion or period of the movement of the engaging member, the first or second switch valve is switched, so that the negative pressure is supplied to one suction nozzle immediately before the one suction nozzle contacts the EC, or the supplying of negative pressure to one suction nozzle is stopped immediately before the EC held by the one suction nozzle contacts the PWB. Thus, one suction nozzle can hold and release an EC at respective appropriate timings, not too early or not too late, so that the EC is reliably taken from the EC supplying device and mounted on the PWB supported by the board supporting device. In addition, since the supplying of negative pressure to one suction nozzle is stopped while the one suction does not hold an EC, the negative pressure does not leak from the one suction nozzle, so that a sufficient amount of negative pressure can be supplied to the other suction nozzle or nozzles which is or are holding an EC or respective ECs.
(12) According to a twelfth feature of the present invention that includes the eleventh feature (11), the each switch valve device is switched, when the second switch valve thereof is switched to the state to stop the supplying of the negative pressure to the one suction nozzle, to a state in which the each switch valve device permits supplying of a positive pressure to the one suction nozzle. When the positive pressure is supplied to one suction nozzle, the one suction nozzle positively releases an EC. Therefore, when the one suction nozzle is moved away from the PWB, the EC does not stick to the one nozzle, so that the EC is reliably mounted on the PWB.
(13) According to a thirteenth feature of the present invention that includes any one of the tenth to twelfth features (10) to (12), the switch valves of the each switch valve device comprises a first switch valve and a second switch valve each of which comprises a spool valve including a spool, and wherein the respective spools of the respective first switch valves of the switch valve devices are provided along a second circle whose center is located on the axis line of the rotatable body and whose diameter is smaller than a diameter of the first circle along which the suction nozzles are provided, and the respective spools of the respective second switch valves of the switch valve devices are provided along a third circle whose center is located on the axis line of the rotatable body and whose diameter is smaller than the diameter of the first circle and is different from the diameter of the second circle, such that the respective spools of the respective second switch valves are alternate with the respective spools of the respective first switch valves in a zigzag pattern in a circumferential direction of the rotatable body. The improvement of EC mounting efficiency may be achieved by decreasing the outer diameter of the rotatable body. The smallest diameter of the first circle along which the suction nozzles are provided, depends on the size (i.e., the greatest diameter) of each suction nozzle and the total number of the suction nozzles. Thus, for decreasing the outer diameter of the rotatable body, it is desirable that the first and second switch valves be provided radially inward of the suction nozzles. That is, it is desirable to minimize the respective diameters of the second and third circles along which the first and second switch valves are provided. To this end, in the present EC mounting system, the respective first spools of the first switch valves are alternate with the respective second spools of the second switch valves in a zigzag or stagger pattern or fashion in a circumferential direction of the rotatable body. The respective diameters of the second and third circles can be decreased for the following reasons: First, the difference between the respective diameters of the second and third circles can be decreased as compared with the case where each pair of first and second spools are aligned with each other in a radial direction of the rotatable body, and accordingly the diameter of the greater or outer one of the second and third circles can be decreased. Second, the diameter of the greater one of the second and third circles can be decreased as compared with the case where the first spools and the second spools are provided along a single or common circle whose diameter must be great. For these reasons, the outer diameter of the rotatable body can be decreased by providing the first spools and the second spools along the second and third circles, respectively, in a zigzag fashion. Consequently the rotatable body can he rotated at higher speeds, and the noise and vibration generated from the body can be reduced. In addition, since only a smaller centrifugal force is exerted to the EC held by each suction nozzle, the EC mounting efficiency can be improved. Moreover, the mass of the rotatable body can be easily decreased, and accordingly the movable member can be moved at higher speeds, which leads to improving the EC mounting efficiency. The thirteenth feature (13) is advantageously combined with the twentieth feature (20) wherein the image taking device simultaneously takes respective images of the ECs sucked and held by the suction nozzles, because the image taking device can be more simply constructed and disposed since all the ECs held by the suction nozzles are contained in a smaller area.
(14) According to a fourteenth feature of the present invention that includes any one of the ninth to thirteenth features (9) to (13), the at least one switch valve of each of the switch valve devices comprises a spool valve comprising a spool which extends in a direction having an angle relative to a horizontal plane, and which is movable to an upper position thereof and a lower position thereof to control supplying of a negative pressure to one of the suction nozzles that corresponds to the each switch valve device; and a spool-downward-movement preventing device which prevents, at at least the upper position of the spool, a downward movement of the spool because of gravity, and permits a downward movement of the spool by engagement of the spool with the valve-engaging portion of the engaging member. The spool is moved downward by engagement thereof with the valve-engaging portion of the engaging member, so that the switch valve is switched from a state in which the switch valve stops the supplying of negative pressure, to another state in which the switch valve allows the supplying of negative pressure. Since the spool-downward-movement preventing device prevents, at the upper position of the spool, a downward movement of the spool because of gravity, the switch valve is not switched by the weight of the spool, but is switched by only the downward movement of the spool caused by the engagement of the spool with the engaging member. At the lower position of the spool, the spool may be supported by a support member which is employed for preventing the spool from moving further downward from its lower position. Alternatively, the spool-downward-movement preventing device may be adapted to prevent, also at the lower position of the spool, a further downward movement of the spool because of gravity. The fourteenth feature (14) may be employed independent of any of the fourth to ninth features (4) to (9), i.e., may be generally or widely employed in a switch valve which is switchable by engagement thereof with an engaging member and which controls the supplying of negative and/or positive pressure to a suction nozzle.
(15) According to a fifteenth feature of the present invention that includes the fourteenth feature (14), the rotatable body has a plurality of spool holes in which the respective spools of the respective spool valves of the switch valve devices are fitted, respectively, and wherein the spool-downward-movement preventing device of the each switch valve device comprises a pressure-based spool-downward-movement preventing device which applies at least one of a positive pressure and a negative pressure, to a local portion of an outer circumferential surface of a corresponding one of the spools in a circumferential direction of the one spool, and thereby presses the one spool against an inner circumferential surface of a corresponding one of the spool holes, so that the one spool is prevented from moving downward, by a frictional force which is produced between the outer circumferential surface of the one spool and the inner circumferential surface of the one spool hole. The pressure-based spool-downward-movement preventing device may be a simple one wherein an air passage which can be closed by one spool crosses a corresponding spool hole, a first portion of the air passage on one side of the spool is connected to a positive- or negative-pressure source, and a second portion of the air passage on the other side of the spool is connected to the atmosphere, or alternatively the first portion of the air passage is connected to a positive-pressure source and the second portion is connected to a negative-pressure source. In either case, in a state in which the spool closes the air passage, different pressures act on diametrically opposite portions of the spool, respectively, so that the pressure difference presses the spool against the inner surface of the spool hole. Otherwise, an air passage may be only partly interfered with by the spool or the spool hole, so that a positive or negative pressure is always present throughout the air passage, i.e., on both sides of the spool. In this case, if a clearance between the spool and the inner surface of the spool hole is communicated with the atmosphere, the positive or negative pressure is only locally applied to a certain portion of the outer surface of the spool in a circumferential direction of the spool, so that the locally applied pressure presses the spool against the inner surface of the spool hole. In the case where the positive pressure acts on the spool, the clearance between the spool and the spool hole may be communicated with a negative-pressure source.
(16) According to a sixteenth feature of the present invention that includes any one of the tenth to fifteenth features (9) to (15), the switch valves of the each switch valve device comprises a first switch valve and a second switch valve each of which comprises a spool valve including a spool, and wherein the rotatable body has a negative-pressure passage through which a negative pressure is supplied to one of the suction nozzles that corresponds to the each switch valve device and which communicates with the first and second switch valves in series, and a positive-pressure passage through which a positive pressure is supplied to the one suction nozzle and which communicates with the second switch valve, and wherein in a state in which the first and second switch valves are positioned at respective upper positions thereof, the negative-pressure passage is closed by the first switch valve and is opened by the second switch valve, and the positive-pressure passage is closed by the second switch valve, and, when the spool of the first switch valve is moved to a lower position thereof from the state, the negative-pressure passage is completely opened, and when the spool of the second switch valve is additionally moved to a lower position thereof, the negative-pressure passage is closed and the positive-pressure passage is opened. In the state in which the first and second switch valves are positioned at their upper positions, one suction nozzle is not supplied with the negative pressure passage or the positive pressure, and cannot suck or hold an EC. When the first spool of the first switch valve is moved to its lower position, the one suction nozzle is supplied with the negative pressure, and sucks and holds an EC. In this state, when the second spool of the second switch valve is moved to its lower position, the one suction nozzle is disconnected from the negative pressure and is supplied with the positive pressure, so that the one suction nozzle positively releases the EC. Since the positive-pressure passage is opened and closed by the second spool of the second switch valve, it is not essentially required that the positive-pressure passage is communicated with the first switch valve. However, the positive-pressure passage may be communicated with the first switch valve, because the shape of the first spool and/or the position of the positive-pressure passage can be so determined that the positive-pressure passage cannot completely be closed by the first spool. For example, in the case where an axis line of the positive-pressure passage perpendicularly intersects an axis line of the first spool, the first spool may include a small-diameter portion which is located in the positive-pressure passage, so that the first spool cannot completely close the positive-pressure passage. Alternatively, the positive-pressure passage may be partly interfered with by the first spool, according to the seventeenth feature (17) described below. In the latter case, the fourteenth feature (14) can be easily employed. The sixteenth feature (16) may be employed independent of any of the fourth to ninth features (4) to (9), i.e., may be generally or widely employed in a switch valve which is switchable by engagement thereof with an engaging member and which controls the supplying of negative and/or positive pressure to a suction nozzle.
(17) According to a seventeenth feature of the present invention that includes the sixteenth feature (16), the positive-pressure passage communicates with the spool hole of the first switch valve, such that the positive-pressure passage is partly interfered with by the spool of the first switch valve, and a clearance between an outer circumferential surface of the spool of the first switch valve and an inner circumferential surface of the spool hole of the first switch valve communicates with a space whose pressure is lower than the positive pressure supplied through the positive-pressure passage, and wherein the positive-pressure passage communicates with the spool hole of the second switch valve, and a clearance between an outer circumferential surface of the spool of the second switch valve and an inner circumferential surface of the spool hole of the second switch valve communicates with a space whose pressure is lower than the positive pressure supplied through the positive-pressure passage. The space whose pressure is lower than the positive pressure may be the atmosphere or the negative-pressure passage. In the present EC mounting system, the first spool of the first switch valve, being positioned at each of its upper and lower positions, does not completely close the positive-pressure passage, and is pressed against the inner surface of the first spool hole by the positive pressure supplied through the positive-pressure passage, so that the first spool is prevented from moving downward. The second spool of the second switch valve, being positioned at its upper position, closes the positive-pressure passage, and is pressed against the inner surface of the second spool hole by the positive pressure, so that the second spool is prevented from moving downward.
(18) According to an eighteenth feature of the present invention that includes the fourteenth feature (14), the spool-downward-movement preventing device comprises a friction ring which is supported by the rotatable body such that the friction ring is not movable relative to the rotatable body and is interference-fitted on the spool, and which prevents the downward movement of the spool, owing to a frictional force which is produced between the spool and the friction ring. The friction ring can prevent the downward movement of the spool, at an arbitrary position in a direction parallel to the axis line of the rotatable body.
(19) According to a nineteenth feature of the present invention that includes any one of the eleventh to eighteenth features (11) to (18), the first and second switch valves include, in addition to respective first engageable portions as the respective engageable portions thereof which are engageable with the valve-engaging portion of the engaging member, respective second engageable portions, and wherein the system further comprises a returning device which is simultaneously engageable with the second engageable portions of the first and second switch valves, to simultaneously return the first and second switch valves to respective initial states thereof in which the first and second switches cooperate with each other to stop the supplying of the negative pressure, and the supplying of the positive pressure, to the one suction nozzle. The returning device simultaneously engages the respective engageable portions of the first and second switch valves, and simultaneously returns the first and second switch valves to their initial states. In the present EC mounting system, the first and second switch valves can be easily and quickly returned to their initial states. The returning device may be, as will be described in DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, one which simultaneously returns all the switch valves of the plurality of switch valve devices of the EC mounting system.
(20) According to a twentieth feature of the present invention, there is provided an electric-component mounting system, comprising a board supporting device which supports a printed-wiring board; a movable member which is movable to an arbitrary position on a movement plane parallel to the printed-wiring board supported by the board supporting device; a main moving device which moves the movable member; a rotatable body which is attached to the movable member such that the rotatable body is rotatable about an axis line thereof perpendicular to the movement plane; a rotatable-body rotating device which rotates the rotatable body about the axis line thereof; a plurality of suction nozzles which sucks and holds respective electric components and which are supported by the rotatable body at respective positions offset from the axis line of the rotatable body; a nozzle moving device which moves at least one of (a) each of the suction nozzles and (b) the board supporting device, toward, and away from, the other of the each suction nozzle and the board supporting device, in a direction perpendicular to the movement plane; an image taking device which simultaneously takes, during a movement of the rotatable body caused by the movement of the movable member by the main moving device, respective images of the electric components held by the suction nozzles, while the image taking device is moved with the rotatable body; and a control device which obtains information by processing the images of the electric components taken by the image taking device, and controls, based on the obtained information, at least one of the main moving device, the rotatable-body rotating device, and the nozzle moving device. The image taking device may be a surface-image taking device which has an image-take surface capable of simultaneously forming respective images of all the ECs. The rotatable body may be rotated to move sequentially the suction nozzles to an EC-suck position, change the current rotation position of the EC held by one suction nozzle, correct a rotation-position error of the EC held by one suction nozzle, and/or shorten a distance of movement of the movable member. Based on the taken image of the EC held by one suction nozzle, the control device may determine at least one position error of the EC held by the one suction nozzle, so that the EC can be mounted with an accurate rotation position, at an accurate EC-mount location on the PWB. The present EC mounting system can enjoy the same advantages as those described in connection with the second and third features (2) and (3).
(21) According to a twenty-first feature of the present invention that includes the twentieth feature (20), the main moving device comprises a slide which is movable in an X-axis direction parallel to the movement plane, and moves, on the slide, the movable member in a Y-axis direction parallel to the movement plane and perpendicular to the X-axis direction, wherein the image taking device is attached with the rotatable body to the movable member, and wherein the system further comprises a reflecting device which is supported by the slide such that the reflecting device is opposed to a path of movement of the rotatable body and the image taking device, and which causes the respective images of the electric components held by the suction nozzles, to be incident to the image taking device. The reflecting device may be provided by a prism which has, as will be described in DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, two reflecting surfaces which are inclined by about 45 degrees, symmetrically with each other, with respect to a plane containing the axis line of the rotatable body; or a mirror which extends perpendicularly to the axis line of the rotatable body. Since the image taking device is attached together with the rotatable body to the movable member, the respective relative positions of the image taking device and the ECs held by tale suction nozzles do not change, so that while the image taking device is moved by the movement of the movable member, it can take respective images of the ECs as if they were still. When the movable member is moved in the Y-axis direction, the ECs pass by the reflecting device provided on the slide. Thus, the ECs can be moved directly to respective target positions, without taking any detours, while respective images thereof are taken by the image taking device. For example, in the case where the board supporting device and an EC supplying device are provided on both sides of the reflecting device in the Y-axis direction, the suction nozzles must pass by the reflecting device, when they are moved to the PWB after they suck and hold respective ECs. Thus, the image taking device can take respective images of the ECs, while the suction nozzles are moved from the EC supplying device to the board supporting device over the shortest distance therebetween. In addition, since the image taking device is moved with the rotatable body, the present EC mounting system does not need an exclusive moving device for moving the image taking device, which leads to simplifying the construction of the system.
(22) According to a twenty-second feature of the present invention that includes the twentieth or twenty-first feature (20) or (21), the control device comprises an error-elimination control portion which determines, based on the information obtained by processing the images of the electric components taken by the image taking device, at least one position error of the electric component held by each of the suction nozzles, and controls at least one of the main moving device and the rotatable-body rotating device to eliminate the determined position error, and thereby eliminate at least one position error of the electric component relative the printed-wiring board on which the electric component is to be mounted.